On Wednesday, November 20, 2019 at 4:47:03 PM UTC-5, Jim Joyce wrote:
On Wed, 20 Nov 2019 12:53:55 -0800 (PST), trader_4
wrote:

On Wednesday, November 20, 2019 at 2:35:33 AM UTC-5, Jim Joyce wrote:
On Tue, 19 Nov 2019 20:10:58 -0800 (PST), trader_4
wrote:

On Tuesday, November 19, 2019 at 10:33:25 PM UTC-5, Jim Joyce wrote:

6. The house has a 240VAC breaker box on the exterior wall, with no room
for an additional breaker, so I'm planning to buy a small 2-circuit
sub-panel that I'd attach to the house, right next to the existing 240VAC
panel. I would ask the electrician to connect the sub-panel to the existing
240VAC panel.

Q: I assume the electrician can create a new circuit from the 240VAC panel.
Are there any issues with that plan?

Should be OK, depending of course on what other loads are on the existing
panel.

That panel is dedicated to the kitchen range, the clothes dryer, and the
HVAC.



Doh! I hope there is enough capacity. Did you add up all the loads compared to the capacity?

No, I did not. Ugh!

IDK, with the sub-panel full and those major loads already on it,
it doesn't sound too good. I hope it's bigger than 100A.

Dryer 30
HVAC 30
Stove 40 or
Ovens + Cooktop 60....










Also, that panel is full, yet the youtube videos all show that a new
breaker is used to feed the sub-panel. However, there's no room for a new
breaker.

I suppose one option would be to use an existing breaker in the main panel
to feed the sub-panel, and then whatever that breaker *was* feeding would
be fed from a new breaker in the sub-panel. I hope I described that
properly.

Yes, that's what you do. Or as Ed suggested, if it's a panel where half
size breakers are available, you could free up space and not need the
additional sub-panel.





Does the new sub-panel need a plywood backer board? It'll be mounted to the
exterior of the (brick) house.

IDK of any code reqt that say so. I think it depends on what the subpanel
is being used for. If it's in a basement and and romex is going to run
into it, then they use a backer board which gives you a place to staple
the cables to as the enter the panel. But I've seen other sub-panels
outside for pools and such that are just mounted directly to the house
siding and where the wires enter and exit via conduit. That' what you'd
have, with the UF cable going through conduit until it gets underground
or if you use conduit and individual wires. With brick exterior, I'd
probably use a backer board, just to keep it off the brick which can be
damp.




If so, does the backer board need to be
painted black? One of the YT videos said some jurisdictions have those
requirements,

Sounds like BS to me. I've seen a lot of them, never saw one painted
black yet. It's not part of the NEC, that's for sure.


but I haven't checked locally. Lastly, what about a separate
ground rod for the sub-panel, or can it get ground from the main panel?


It has to be grounded from the main panel. The ground and neutral also
remain separate at the sup-panel.


This is starting to get complicated.

It will be more so if there isn't enough capacity in that sub-panel.